Troubleshooting of Local Area Networks (LANs) requires that the technician have considerable knowledge of how the network functions, including the protocols of the network. In addition, they must have detailed knowledge of each type of message sent over the network, and the implications of each particular type of message being sent. This problem is more severe if a technician must trouble shoot more than one type of LAN, thus they must become familiar with each different protocol.
The cable length for a local area network is an important parameter since all local area networks are limited in the distance over which signals can be sent. Thus, intermittent problems are common if this length is exceeded. For some types of local area networks, the length for a given segment will be static unless a new station is installed or an older station is removed from a segment. However, with a Token-Ring type local area network, the electrical length of the cable within a ring varies each time a station is activated or deactivated. This occurs because activation of a station causes the cable between the station and a media access unit (MAU), to which the station attaches, to be electrically inserted into the ring. Deactivation electrically removes this section of cable from the ring.
This change in cable length due to activating and deactivating stations can cause intermittent problems on a ring of the network. Each station within this type of network repeats each signal received before sending the signal to the next station, thus the cable distance between stations is the limiting factor in the size of the ring. If several adjacent stations are deactivated, particularly when all stations connected to a single MAU are deactivated, the length between active stations can exceed the specifications of the network, which can cause intermittent failures. Thus it is important in troubleshooting a Token-Ring network to be able to ascertain the cable length between all the active stations.
In prior art systems, the only known way to measure the length of a Token-Ring network is to use a time domain reflectometer device while the network is inactive. When the network is inactive, however, the stations are not electrically connected to the network. Thus, there is no prior art way to measure the actual length of an active Token-Ring local area network while it is active.
Of course the length can be measured by physically measuring the length of cable between each station and the MAU, measuring the length of cables between each MAU in the ring, manually determining which stations are actively connected to the network at the time the length is to be measured, and then manually adding the length of the cable between the multiple excess units and the cable length for each of the stations that is currently active. This is a time consuming process and prone to errors.
There is need in the art then for a way of measuring the length of a Token-Ring local area network while that network is active.